1. Field of the Invention
The present invention relates to an overshoot detection circuit for a voltage regulator.
2. Description of the Related Art
A conventional voltage regulator is now described. FIG. 4 is a circuit diagram illustrating the conventional voltage regulator.
The conventional voltage regulator includes a power supply terminal 1, a ground terminal 2, an output terminal 3, a reference voltage circuit 10, a differential amplifier circuit 20, an overshoot detection circuit 30, PMOS transistors 31 and 40, and resistors 51 and 52.
The overshoot detection circuit 30 compares a feedback voltage divided by the resistors 51 and 52 with a reference voltage of the reference voltage circuit 10. Then, when the feedback voltage is lower than the reference voltage, the overshoot detection circuit 30 outputs HIGH to turn off the PMOS transistor 31. When an overshoot occurs in an output voltage of the output terminal 3 and the feedback voltage becomes higher than the reference voltage, the overshoot detection circuit 30 outputs LOW to turn on the PMOS transistor 31. As a result, the PMOS transistor 40 is turned off, and hence the overshoot can be prevented from being larger (see, for example, Japanese Patent Application Laid-open No. 2005-301439).
However, the conventional technology has the following problem.
In order to increase the response speed of the overshoot detection circuit 30, it is necessary to supply a sufficient current to the overshoot detection circuit 30 all the time. Thus, the current consumption is increased. If the current consumption of the overshoot detection circuit 30 is suppressed, the response speed of the overshoot detection circuit 30 is reduced, and hence it becomes difficult to suppress the overshoot quickly.
The present invention has been made in view of the above-mentioned problem, and provides a voltage regulator that includes an overshoot detection circuit having high response speed with low current consumption.